#
#  Copyright 2009-2016, Jack Poulson
#  All rights reserved.
#
#  This file is part of Elemental and is under the BSD 2-Clause License,
#  which can be found in the LICENSE file in the root directory, or at
#  http://opensource.org/licenses/BSD-2-Clause
#
include(FindCXXFeatures)
include(CheckCXXSourceCompiles)

message(STATUS "CXX11_COMPILER_FLAGS=${CXX11_COMPILER_FLAGS}")
message(STATUS "CXX14_COMPILER_FLAGS=${CXX14_COMPILER_FLAGS}")
set(CMAKE_REQUIRED_FLAGS ${CXX14_COMPILER_FLAGS})

# TODO(poulson): Test for C++14 features such as [[deprecated]]

# Required features
# =================
set(ALIAS_CODE
    "#include <complex>
     template<typename Real>
     using Complex = std::complex<Real>;
     int main()
     {
         Complex<double> a;
     }")
check_cxx_source_compiles("${ALIAS_CODE}" EL_HAVE_TEMPLATE_ALIAS)
if(NOT EL_HAVE_TEMPLATE_ALIAS)
  message(FATAL_ERROR "C++11 template aliasing not detected. You may want to make sure that your compiler is sufficiently up-to-date (e.g., g++ >= 4.7)")
endif()

# Standard but inconsistently supported features
# ==============================================
set(STEADYCLOCK_CODE
    "#include <chrono>
     int main()
     {
         std::chrono::steady_clock clock;
         return 0;
     }")
set(NOEXCEPT_CODE
    "#include <vector>
     void Foo( const std::vector<int>& x ) noexcept { }
     int main()
     { return 0; }")
check_cxx_source_compiles("${STEADYCLOCK_CODE}" EL_HAVE_STEADYCLOCK)
check_cxx_source_compiles("${NOEXCEPT_CODE}" EL_HAVE_NOEXCEPT)

# C++11 random number generation
# ==============================
# Note: It was noticed that, for certain relatively recent Intel compiler
#       releases, the following snippets will suggest that normal distributions
#       are supported, but not uniform integer or real distributions. 
#       Unfortunately, it has been observed that, when one attempts to sample
#       from a normal distribution, the application hangs indefinitely.
#       Thus, Elemental takes the approach of requiring all of the following
#       to be detected before any are used.
set(NORMAL_CODE
    "#include <random>
     int main()
     {
         std::random_device rd;
         std::mt19937 mt(rd());
         std::normal_distribution<double> dist(0,1);
         const double x = dist(mt);
         return 0;
     }")
set(UNIFORM_INT_CODE
    "#include <random>
     int main()
     {
         std::random_device rd;
         std::mt19937 mt(rd());
         std::uniform_int_distribution<int> dist(0,10);
         const int x = dist(mt);
         return 0;
     }")
set(UNIFORM_REAL_CODE
    "#include <random>
     int main()
     {
         std::random_device rd;
         std::mt19937 mt(rd());
         std::uniform_real_distribution<double> dist(0,1);
         const double x = dist(mt);
         return 0;
     }")
check_cxx_source_compiles("${NORMAL_CODE}" EL_HAVE_NORMAL_DIST)
check_cxx_source_compiles("${UNIFORM_INT_CODE}" EL_HAVE_UNIFORM_INT_DIST)
check_cxx_source_compiles("${UNIFORM_REAL_CODE}" EL_HAVE_UNIFORM_REAL_DIST)
if(EL_HAVE_NORMAL_DIST AND 
   EL_HAVE_UNIFORM_INT_DIST AND
   EL_HAVE_UNIFORM_REAL_DIST)
  set(EL_HAVE_CXX11RANDOM TRUE)
else()
  set(EL_HAVE_CXX11RANDOM FALSE)
endif()

# "restrict" support
# ==================
set(RESTRICT_CODE "int main() { int* RESTRICT a; return 0; }")
set(CMAKE_REQUIRED_DEFINITIONS "-DRESTRICT=__restrict__")
check_cxx_source_compiles("${RESTRICT_CODE}" EL_HAVE___restrict__)
set(CMAKE_REQUIRED_DEFINITIONS "-DRESTRICT=__restrict")
check_cxx_source_compiles("${RESTRICT_CODE}" EL_HAVE___restrict)
set(CMAKE_REQUIRED_DEFINITIONS "-DRESTRICT=restrict")
check_cxx_source_compiles("${RESTRICT_CODE}" EL_HAVE_restrict)
if(EL_HAVE___restrict__)
  set(EL_RESTRICT "__restrict__")
  message(STATUS "Using __restrict__ keyword.")
elseif(EL_HAVE___restrict)
  set(EL_RESTRICT "__restrict")
  message(STATUS "Using __restrict keyword.")
elseif(EL_HAVE_restrict)
  set(EL_RESTRICT "restrict")
  message(STATUS "Using restrict keyword.")
else()
  set(EL_RESTRICT "")
  message(STATUS "Could not find a restrict keyword.")
endif()

# __PRETTY_FUNCTION__ support
# ===========================
set(PRETTY_FUNCTION_CODE
    "#include <iostream>
     int main()
     { 
         std::cout << __PRETTY_FUNCTION__ << std::endl;
         return 0;
     }")
check_cxx_source_compiles("${PRETTY_FUNCTION_CODE}" EL_HAVE_PRETTY_FUNCTION)

unset(CMAKE_REQUIRED_FLAGS)
unset(CMAKE_REQUIRED_DEFINITIONS)